1. Field of the Invention
The present invention relates to systems that employ hydraulic, pneumatic or other types of valves and, in particular, relates to systems for controlling and monitoring the operation of such valves.
2. Background of the Invention
In many industrial and other systems, hydraulic, pneumatic or other types of valves are employed to turn a machine off and on. Such valves can be employed either singly, or in redundant pairs in order to limit the impact that any single failure of a single valve could have upon the overall system""s operation.
The machine(s) downstream of the valve(s) sometimes need servicing. Typically the valve(s) must be turned off before the machines can be serviced. Therefore, before a person accesses the machine to perform such a repair, it is desirable to verify that the fluid pressure to the machine has been shut off. For example, it is desirable that a signal be provided indicating that the fluid pressure has been successfully shut off.
A pressure sensor, or more than one redundant pressure sensor, can be positioned to determine whether the fluid pressure has been shut off. Nevertheless, such pressure sensors can themselves occasionally malfunction. For example, a pressure sensor output contact designed to open when the fluid pressure is above or below a given threshold may become welded in a particular state. Also, the sensor may become stuck or broken.
If the signal indicating whether the fluid pressure has been successfully shut off is based upon such a welded pressure sensor output, the signal may incorrectly indicate that the fluid pressure has been shut off even when this is not the case. Also, because of redundancy within the system design, it is possible that the malfunctioning sensor would go undetected (and erroneous signals would be provided) for a long period of time. Additionally, when multiple pressure sensors are being employed, it may be difficult to determine which of the multiple pressure sensors is malfunctioning even when it is realized that one of the sensors is malfunctioning.
Therefore, it would be advantageous if a system could be developed for controlling and monitoring the status of valves in a system employing hydraulic, pneumatic or other types of valves. In particular, it would be advantageous if the control/monitoring system avoided providing an indication that the valves were closed in situations where one of the pressure sensors used to determine the valves"" status was malfunctioning. Additionally, it would be advantageous if, in the case of a failure of one of the pressure sensors, the control/monitoring system was able to prohibit the servicing of the machine (at least by providing a signal indicating to a technician that he or she should not be servicing the machine). Further, it would be advantageous if the control/monitoring system was able to provide information that could be used to identify the malfunctioning pressure sensor or the valve. Additionally, it would also be advantageous if such a control/monitoring system could be developed that was not significantly expensive to implement.
The present inventors have discovered a new system for controlling and monitoring a valve system that is capable of determining whether a malfunction has occurred in a pressure sensor used to determine valve status. In addition to the pressure sensor(s) themselves, actuator(s) for the valve(s), and a switch or turning on and off the valve(s), the control/monitoring system further includes a detection device/circuitry that monitors the behavior of the sensors. When a sensor malfunction is detected, the detection device precludes the overall control/monitoring system from indicating that the valve(s) have been closed/isolated, even though the valve(s) may in fact be shut off, which is indicative of the sensor malfunction. Depending upon the number and configuration of indications that are provided by the control/monitoring system, the system is further able to provide an indication of which of the pressure sensors is malfunctioning.
In at least some embodiments of the control/monitoring system, each of the pressure sensors includes multiple contacts that are actuated in response to changes in the pressure being sensed by the sensors. In order for the system to provide an indication that valve(s) of the valve system have been turned off (isolated), the pressure sensors must first be in a first state when the valve(s) are turned off, where that first state is indicative that the valve(s) are open, and then the pressure sensors must switch to a second state that is indicative that the valve(s) have been closed. By requiring that the pressure sensors both begin in the first state but then switch to the second state, the control/monitoring system guarantees that the pressure sensors are properly sensing and responding to changes in the delivered pressure, such that it is appropriate to output indications of valve status based upon the output of the pressure sensors.
In particular, the present invention relates to a system for controlling and monitoring the operation of a valve. The system includes a valve actuator and a switch that, upon being actuated, provides a control signal to the valve actuator designed to cause the valve to change from a first valve state to a second valve state. The system further includes a first sensor positioned downstream of the valve, a first output indicator, and a sensor failure detecting device coupled at least indirectly to the switch, the first sensor and the first output indicator. When not detecting a sensor failure, the sensor failure detecting device allows the first output indicator to indicate that the valve has changed from the first valve state to the second valve state in response to the switch being actuated when the sensor indicates that the valve has so changed. Upon detecting a sensor failure, the sensor failure detecting device prevents the output indicator from indicating that the valve has changed from the first valve state to the second valve state in response to the switch being actuated.
The present invention further relates to a system comprising a flow-governing device, an actuator for controlling a status of the flow-governing device, and first and second sensors that operate to sense the status of the flow-governing device. The system further includes means for receiving commands to change the status of the flow-governing device, for providing a control signal to the actuator in response to the received commands, for receiving signals from the sensors, for detecting when a sensor malfunction has occurred, and for providing at least one output indication indicative of the sensor malfunction when the sensor malfunction has occurred.
The present invention additionally relates to a method of monitoring whether a valve has been shut off in response to a command. The method includes causing at least one switching element of an electric circuit to change a state in response to the command. The method further includes energizing a coil in response to the changing of the state of the at least one switching element, where the energizing of the coil only occurs if a sensor component is in a first position indicating that the valve has not been shut off. The method additionally includes energizing an indicator light in response to the energizing of the coil, where the energizing of the indicator light only occurs if the sensor component switches, subsequent to the energizing of the coil, from the first position to a second position indicating that the valve has been shut off.